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Biomedical subjects

G M Simmons

Publications and source records attributed to G M Simmons.

25 records · Page 2Linked to original sources
PubMed1985

Cryoconite holes on glaciers.

Cryoconite holes are water-filled depressions on the surface of glaciers. They contain microbial communities and may contribute to glacial wastage and biological colonization of ice-free areas.

Antarctic Regions↗
PubMed1984

Enhanced visualization of soft tissues in the study of aborted fetuses through the use of xeroradiography.

As part of the diagnostic workup following an episode of fetal loss, it is generally recommended that fetal tissue be submitted for chromosome analysis and that the fetus be photographed and radiographed. Our recent clinical experience has suggested that, in those fetuses where size is compatible, xeroradiography may be superior to standard radiography. Xeroradiography utilizes principles similar to those in film radiology, with low-energy photon beams and relatively long exposure times. The physical characteristics of the beam and imaging system provide optimal soft tissue visualization. We have found this technique to be of use in studying a broad variety of abortuses with abnormalities. Examples of fetal abnormalities in which we have used this technique include acardia, neural tube defects, nuchal cystic hygroma, and arthrogryposis. In fetuses weighing 500-1,000 gm, the exposure settings are 25 MA, 1 second, 40 KVP. For larger fetuses the KVP should be increased by 1 or 2. This technique has not been useful for a complete body view of large fetuses due to the size limitations of the xeroradiographic cassette itself.

Anencephaly↗
PubMed1984

Response of an antarctic lake heterotrophic community to high dissolved oxygen.

The upper waters of Lake Hoare, Antarctica, contain dissolved oxygen at about three times the normal saturation (>/=42 mg liter). The response of the heterotrophic plankton community to this high dissolved oxygen was evaluated by the criteria of CFU and d-[U-C]glucose assimilated-respired. High dissolved oxygen was not inhibitory to d-[U-C]glucose assimilation-respiration compared with normal atmospheric dissolved oxygen in Lake Hoare water. The d-[U-C]glucose was assimilated and respired optimally at 12 degrees C in Lake Hoare. The d-[U-C]glucose assimilated-respired in the upper saturated atmospheric dissolved oxygen waters of Mountain Lake, Va., was inhibited in contrast to Lake Hoare (P < 0.05). CFU formation was inhibited in both lakes. CFU represent <1% of the fluorochrome-stained direct counts in Lake Hoare. Lake Hoare planktobacteria are smaller than the planktobacteria in Mountain Lake. ATP size fractionation revealed that 39% of the ATP biomass was <0.5 mum in Lake Hoare.

Journal Article↗
PubMed1983

Sensitivity of an oligotrophic lake planktonic bacterial community to oxygen stress.

Dissolved oxygen at approximately four times normal saturation (42 mg liter) inhibited the growth and metabolism of summer planktonic bacteria in the surface water of alpine oligotrophic Mountain Lake (Giles County, Va.). Data were derived from growth of CFU on membrane filters, d-[U-C]glucose incorporation into the extractable lipid of these CFU, and respiration and assimilation of d-[U-C]glucose by lake water samples. Statistically significant (alpha < 0.05) differences were not detected in either CFU or C incorporation in lipid when superoxide dismutase (30 U ml) or catalase (130 U ml) was added to the medium. Thus, exogenous oxygen by-products apparently are not responsible for the observed inhibition of growth and metabolism.

Journal Article↗
PubMed1981

Characteristics of the Drosophila paulistorum Male Sterility Agent in a Secondary Host, Ephestia kuehniella.

Crosses among the six semispecies of Drosophila paulistorum produce sterile male hybrids. This sterility is caused by an agent which has characteristics of a microorganism. It is pathogenic in a secondary host, the larvae of the Mediterranean meal moth, Ephestia kuehniella, and can be serially passaged in Ephestia, where it is lethal. The agent was passaged back into D. paulistorum, where it induced sterility in males of a semispecies different from that of origin of the agent. Infectious particles were obtained from an extract of infected Ephestia by ultracentrifugation in a sucrose-Ficoll-metrizamide gradient. Both crude and purified extracts were lyophilized and stored indefinitely without loss of killing power. The agent was destroyed by low pH, lipid solvents, ultraviolet light, and exposure to a temperature of 56 degrees C for 30 min. It appeared to be sensitive to tetracycline and insensitive to penicillin, suggesting that the agent is not a virus, but more likely a cell wall-deficient bacterium or mycoplasma-like organism.

Journal Article↗